No, the FFP stick won't work without a small change change. Each type of hardware has it's own checkfile, for the single disk Medion it's STG212_check_file. If the box supports usb_key_func.sh, you'll have to guess how the file should be called (STG222_check_file or STG223_check_file might be a good guess), or have a look in the firmware. To get access to the firmware you either have to have telnet or ssh access, or firmware (update) file from Medion/Aldi.

I am fiddling with the same device. Being a newbie at getting in such devices, and do not want to destroy it immediately.

- not so sure about the login, tried with putty both ssh and telenet but it does not react. Suppose I need that backdoor prodcedure? would anybody mind describing that in some detail?
- was a bit disappointed that one cannot open the cabinet as medion tells me that then warranty is void and blablabla, so you need to send the device in, not sure they will be able to get my data back. In case one of the disks breaks I would like to be able to replace the bad disk myself and have the data regenerated. Does anybody have a procedure at hand how to do this?

Are you sure ssh doesn't react? bart107 told the NAS runs HipServ OS from Axentra. Some googling on 'HipServ OS ssh' shows pages like this, which only tells which password to use, and not how to enable the ssh server.
bart107 also only mentioned the password, and I guess he would have told if some trick was needed to enable the ssh server, unless it's obvious, like just enabeling it in the webinterface.

The same OS seems to be running on a number of NASses, among which the Netgears. So I guess exchanging a disk is as easy as plugging in a new one (as least as big as the old one), and power the box up. Maybe you'll have to acknowledge the rebuild in the webinterface.

When trying harder it does seem to react to SSH, so that is good news! Now I face the problem of constructing the login. Not sure which of the numbers I need to use for doing that. On the box itself it has e.g a MSN, a MD a YC and a SN number. tried all of those in the syntax:

username_hipserv_medion_numberabove@IP#

note that while googling I find also a lot of "hipserv2" examples.

I know the user I think that was the first one I created when I installed the box.

Indeed the MEDION LifeCloud uses the hipserv OS. Seems you have quickly found your "product name" of medion which will help you gain SSH access. To gain SSH access, you must be using an admin account, regular users are refused via SSH.